Method for clarifying fats and oils



July 19, 1966 M. E. GRUVER, JR

METHOD FOR CLARIFYING FATS AND OILS Filed Oct. 29, 1962 FIG. 3

FEED

FWATER FIG- 2 INVENTOR. MORRIS E GRUVER JR.

ATTORNEY United States Patent 3,261,546 METHOD FOR CLARIFYING FATS ANDOILS Morris E. Grover, .lr., Rochester, N. assignor t0 Pfaudler FermutitInc, Rochester, N.Y., a corporation of New York Filed Oct. 29, 1962,$er. No. 233,675 2 Claims. (til. 233-20) This invention relates to amethod for purifying rendered oils and fats and, more particularly, forremoving the solid suspended protein-like material from rendered fatsand oils in order to produce a clarified, solid free material.

In the manufacture of fats and oils, the animal waste materialcomprising fat, scraps of bone and meat, and other protein like wastematerial is placed in a vessel and subjected to high tempeartures forextended periods of time. This process is known as dry rendering andseparates the fats and oils from the protein like material. The productof this process consists of the fats and oils in liquid form combinedwith a more or less finely divided mass of solid material comprisedmainly of .protein Waste material. This protein waste material must beseparated from the fats in order to produce a commercially acceptableclear product. The principal object of this invention is the provisionof a more practical, economical and controllable process foraccomplishing this end.

One of the most common methods of removing the protein waste materialfor clarifying has been to centrifuge the products as it comes from therendering kettles. This is an efiicient method of effecting theseparation since the protein-like matter differs from the fats and oilsin specific gravity and can be removed in the form of a heavy sludge,the fats and oils being taken off as the light, or low density,fraction. However, since the raw material used in this process consistsof animal wastes, they are seldom uniform in character or composition,and the amount of protein-like waste material in any given batch of thismaterial can differ markedly; some batches contain very little wastewhile others may contain a great deal. This has imposed a difficultproblem of control of the clarifying or solids removal step since theamount of impurities may differ markedly from batch to batch orthroughout the run of any given batch.

The centrifuges used for the clarification step are generallysemi-continuous in character; that is, a continuous stream of renderedimpure fat is fed to the centrifuge and a continuous stream of clarifiedfat is takenoft the outlet while the protein like solid materialsaccumulate in the centrifuge basket in the form of sludge. The sludgeeventually builds up to the point where it fills the basket andpartially overflows into the clarified fat or effluent conduit andcontaminates the same. At this point, the centrifuge feed must bestopped and steps taken to remove the sludge from the basket before theoperation can be continued. This step, known in the trade as desludging,is performed by various means depending on the centrifuge design. Mostcentrifuges have means for automatically performing this step uponactuation of suitable controls.

Heretofore, the difficulty has been in determining the frequency fordesludging. Since the product is non-uniform in character, thisdesludging operation cannot be efficiently performed on a time basissince an arbitrary time cannot be set wherein sufiicient sludge willbuild up to cause contamination of the product. If desludging is donetoo frequently, the centrifuge is not utilized to its full capacity;this results in an increase in the cost for this operation. On the otherhand, if desludging is not performed sufficiently frequently,contamination of the product results. It is therefore highly desirableto pro- 3,21,546 Patented July 19, 1966 vide a means for reliablydetermining the proper time for desludging in order to utilize thecapacity of the centrifuge to the fullest extent, and to avoidinterrupting the process or clarification more frequently thannecessary, and at the same time to assure the absence of impurities inthe clarified product. The provision of such a means is therefore. aprincipal object of this invention.

In the past, many attempts have been made to provide automatic controlof a fat clarifying centrifuge by means of an instrument which woulddetect the pressure of minute amounts of sludge or other impurity in theproduct and then actuate a control for desludging the machine. Inparticular, since the sludge and the oil differ in density, densitymeasuring instruments have been applied to the output line of suchclarifying centrifuge. However, the difference in density between theoil and the impurities is small, and no such instrument was capable ofdetecting a minute amount of impurity so as to actuate the desludgingcycle before a substantial amount of impurity was passed into theproduct. Similar attempts to measure turbidity and other properties ofthe effluent clarified oil to detect the first amounts of impuritiescoming from the centrifuge have been equally unsuccessful because of thegreat sensitivity needed to detect the first minute amounts of sludge inorder to initiate the desludging cycle sufficiently quickly to avoidcontamination of the prodnet.

I have found, however, that the sludge or solid products resulting fromthe clarification of rendered animal fats and oils consists almostwholly of protein matter which has been reduced to a finely dividedstate by the cooking process in the rendering kettles. Moreover, I havefound that this protein has a high afiinity for water, and will absorbmany times its own weight of water and carry the same through theprocess. Moreover, it is a well known fact that water has a radicallydifferent dielectric constant from oils and fats and that, therefore,even minute amounts of water (less than .I%) can be detected in streamsof oil by means of capacitance meters of known construction. It is,therefore, a further object of this invention to utilize these variousproperties in order to provide a method for preventing minute amounts ofsolid material to be carried over into clarified rendered fats and oilsin order to initiate the desludging cycle of the clarifying centrifugeas soon as sludge begins to appear in the clarified oil product lines.

Other objects of the invention include provision of method forautomatically measuring the quality of the clarified fats and oils andshutting down the feed and desludging the centrifuge Whenever thequality falls below a predetermined value.

Further objects include the provision of means for accomplishing theseobjects which are simple, inexpensive, positive in operation andcompletely automatic.

Other objects and advantages of this invention will be particularly setforth in the claims and will be apparent from the following description,when taken in connection with the accompanying drawings, in which:

FIG. 1 is a schematic flow diagram partly in section, showing acentrifugal clarifying apparatus embodying the present invention.

FIG. 2 is a fragmentary view of the centrifuge of FIG. 1 showing theaccumulation of oil, water and impurities.

FIG. 3 is a fragmentary view similar to FIG. 2 showing the centrifuge indischarging position.

Referring to the drawings, 10 (FIG. 1) indicates a centrifuge of a typegenerally used for clarifying fats and oils and removing protein solidmatter. This centrifuge forms no part of the present invention and isadequately described in the patent to Nyr-op No. 2,578,- 484 issuedDecember 11, 1951. However, a brief description of this centrifuge willbe given at this point in order to clarify the operation of thisinvention.

The raw products to be purified are fed through a stationary pipe 12which extends axially into a rotating bowl 14 of centrifuge 10. The feedtravels downwardly and outwardly, as shown by the arrows, into the rorating bowl where the heavier fractions move to the outside under theinfluence of centrifugal force, while the lighter fractions aredisplaced inwardly toward the axis of rotation. When the bowl has filledwith material, the lighter fractions overflow through annular opening 16(FIG. 2) whence they pass into the clarified product line 18 (FIG. 1).The heavier fraction or sludge remains near the periphery of bowl 14until it is removed as hereinafter described.

A series of openings 20 are formed near the portion of largest diameterof the bowl. These openings are sealed by means of an axially moveablering shaped piston 22 supported in an annular groove 24 adjacent toopenings 20. The piston is maintained in position by means of hydraulicpressure in groove 24. When it is desired to desludge the bowl, suitablecontrols are actuated to relieve the hydraulic pressure in groove 24holding piston 22 in upward position (as shown in FIG. 1) and the pistonmoves downwardly uncovering openings 20 (to the position shown in FIG.3). The contents of the bowl then fly outwardly through openings 20under the influence of centrifugal force. When the bowl has thus beendesludged, the hydraulic pressure is reintroduced to groove 24, movingpiston 22 upwardly to a position covering openings 20 and the centrifugeis ready for another cycle. The mechanism constituting this centrifugeand the controls for actuating the desludging operation are described indetail in the above mentioned Nyrop, No. 2,578,484.

As the bowl of the centrifuge fills with the product, the centrifugalforce causes a separation into two or more layers. The outer layer Swill comprise the heaviest material which is the impurities or sludgecomprising finely divided protein like matter. If sufiicient water hasbeen added to the mass, a second water layer W may also build up, butthis is not necessarily the case. The inner or lightest layer willcomprise the clarified oil. As the bowl begins to fill, the clarifiedoil begins to pass outwardly through annular opening 16 into oildischarge pipe 18 whence it flows to the finished product storage tanks.

A capacitance product analyzer has been placed in the finished productline. The capacitance product analyzer is a known article, commerciallyavailable, and forms no part of this invention. This unit is more fullydescribed by Patents 2,720,624 and 2,717,347 and need not be fullydescribed here. It is sufficient to say that the capacitance of thesensing head 26 of the instrument which is immersed in the product line,is a function of the dielectric constant of the product flowing betweenspaced insulated electrodes just as the capacitance of any condenser isa function of the dielectric constant of the insulating material betweenthe plates. A tuned electronic oscillator 28 is provided whichoscillates freely as long as the capacitance of the sensing head ismaintained at a pre-determined value. However, as soon as thecomposition of the material between the electrodes changes, thecapacitance of the sensing head 26 changes, and the resonance of thetuned circuit is destroyed. This actuates an electrical relay 30 whichin turn can be used to actuate the centrifuge controls to shut off ofthe product line and desludge the centrifuge.

As bowl 14 fills with sludge (or sludge and water).

the oil interface moves progressively inwardly, towards the axis ofrotation, to the position shown in FIG. 2. At this time, small amountsof Water (or water saturated sludge) begin to pass out through opening16 into line 18.

It is Well known that the dielectric constant of oil and water areconsiderably different. Water, particularly in the impure state, is afair conductor of electricity; dry oil is a good insulator with a veryhigh dielectric constant. Thus, it has been found that the inclusion ofas little as .1% moisture in a stream of oil can readily be detected bythe change of the capacitance controller such as that described in theabove mentioned patents.

An important point of this invention is the addition of water to thestrongly hydrophylic protein-like base material prior to centrifuging.The protein immediately absorbs the Water, swelling to several times itsoriginal volume. Thus, the inclusion of even a small amount of theprotein like impurity with its absorbed water in the product line willbe suflicient to actuate the capacitance relay to initiate thedesludging cycle.

Upon initiation of the desludging cycle, relay control 30 shuts off theflow of impure rendered oil to the centrifuge and initiates the downwardmovement of the cylindrical piston 22. This uncovers openings 20 of thecentrifuge and causes the sludge contained in bowl 14 to fly out asshown in FIG. 3. As soon as the centrifuge has been completelydesludged, control 30 causes cylindrical piston 22 to move axially tocover ports 20, and at the same time, open the valve to initiate theflow of raw impure oil to the centrifuge and the cycle is repeated.

Thus, it can be seen that this invention attains its stated objects. Thecycle is completely automatic and acts to desludge the centrifuge assoon as even a minute amount of impurity appears in the clarified oilproduct line. The sensitivity of the capacitance controller in detecting water saturated protein impurities is such that no significantamount of impurity can pass through the controller to the finishedproduct line before the desludging cycle is initated. At the same time,the operation of the centrifuge by a desludging cycle is avoided untilthe centrifuge has removed all the impurities it can contain and thus,the centrifuge is utilized to the highest possible eflficiency. Theapparatus is simple, economical and reliable and operates fullyindependently of any human control.

While I have shown and described the preferred form of mechanism of myinvention it will be apparent that various modifications and changes maybe made therein, particularly in the form and relation of parts, withoutdeparting from the spirit of my invention as set forth in the appendedclaims.

I claim:

1. A method for clarifying dry rendered fat containing hydrophylicimpurities comprising the method steps of adding water to the saidimpure fat, centrifuging impure said fat-water mixture for separatingsaid dry rendered fat from water and impurities, continuously drawingoff said separated fat from said centrifuge, measuring the dielectricconstant of said separated fat to detect the presence of water, andremoving the accumulated impurities and water from said centrifuge whenwater is detected in said separated fat.

2. A method for separating immiscible high and low density components oftheir mixture comprising the method steps of adding an additionalcomponent to said mixture, said additional component having a dielectricconstant differing from said low density component and a densityintermediate said high and low density components, and said additionalcomponent being immiscible in said low density component, centrifugingsaid mixture and said additional component to separate said low densitycomponent from said high density component and said additionalcomponent, continuously drawing off said low density component from saidcentrifuge, measuring the dielectric constant of the low densitycomponent material drawn off to detect the presence of said additionalcomponent therein, and removing the accumulated high density componentand additional component 5 6 from said centrifuge when said additionalcomponent is 2,823,215 2/ 1958 Downing 260412.6 detected in saidmaterial drawn off. 2,933,657 4/ 1960 Maltby et a1 324-61 3,013,57212/1961 Lahti et a1. 137-93 References Cited by the Examiner 3,020,1602/ 1962 Downing et a1. 260--412.6 X Steinbacker 2,216,680 10/1940Thurman 260428 FOREIGN PATENTS 2,467,742 4/1949 HEIIIIIO 233-20 105 4799 1942 Sweden 2,532,792 12/1950 Svensjo 23319 2,576,253 11/1951 Farrellet al. 13793 10 M. CARY NELSON, Primary Examiner. 2,578,484 12/1959Nyrop 23320 2,618,644 11/1952 Bailey 260 428 CHARLES PARKER Exammer' 2628 023 2 1953 Dahlstedt 33 19 A. SUTTO, H. KLINKSIEK, AssistantExaminers.

1. A METHOD FOR CLARIFYING DRY RENDERED FAT CONTAINING HYDROPHYLICIMPURITIES COMPRISING THE METHOD STEPS OF ADDING WATER TO THE SAIDIMPURE FAT, CENTRIFUGING IMPURE SAID FAT-WATER MIXTURE FOR SEPARATINGSAID DRY RENDERED FAT FROM WATER AND IMPURITIES, CONTINUOUSLY DRAWINGOFF SAID SEPARATED FAT FROM SAID CENTRIFUGE, MEASURING THE DIELECTRICCONSTANT OF SAID SEPARATED FAT TO DE-